Full-Stack & Mobile Dev for HOP Logistics

Job Title: Full-Stack & Mobile Development Team / Senior Engineers (Flutter + NestJS + React) for Freight Logistics Platform (HOP)
Project Overview
We are building HOP, an end-to-end digital freight matching and logistics platform tailored for the Indian road logistics sector. The system is built around a single backend architecture powering 5 unified client surfaces and driven by a strict, event-driven 14-state trip lifecycle and an automated double-entry escrow ledger.
We are hiring experienced freelance engineers, technical leads, or a boutique agency to execute our locked architecture across 15 two-week sprints.
Platform Surfaces & Scope of Work
You will build five distinct product surfaces operating off a unified modular backend and a shared phone + OTP authentication system:
* HOP Driver App (Flutter / Android-first):
* Optimized for low-end hardware (sub-3s cold start on 2 GB RAM, APK under 25 MB).
* 6-language vernacular localization (English, Hindi, Marathi, Gujarati, Tamil, Telugu) with Text-to-Speech (TTS) voice alerts.
* Phone GPS location tracking via background foreground service, offline SQLite ping queuing, backdated pings, and gate geofencing.
* In-app trip execution, photo POD capture, and receiver OTP verification.
* HOP Fleet App (Flutter / iOS & Android):
* Mobile companion for fleet owners/managers to bid, track live fleet maps via WebSockets, and assign drivers/trucks.
* HOP Shipper App (Flutter / iOS & Android):
* Load posting, live bidding desk, escrow payments, real-time tracking, and receiver OTP delivery flows.
* HOP Console (React / Desktop-first Web):
* Advanced operations desk for fleet owners and shippers: load board, bidding desk, fleet maps, team seats, invoicing, GST/e-way bills, and ledger exports.
* HOP Admin Console (React Web):
* Internal ops tool for user/transporter verification, dispute handling, trip manual state control, financial reconciliation, and platform audit logs.
Core Backend & System Features
* Modular Monolith Architecture: NestJS, PostgreSQL (system of record), Redis (live state, caching, BullMQ queues), and a dedicated WebSocket gateway for live tracking and bids.
* Strict State Machine: 14 trip lifecycle states (from DRAFT to CLOSED) driven by append-only event logs with row locks.
* Automated Financial Engine: Escrow payment gateway integration (Razorpay Route / Cashfree Easy Split), split payouts, TDS compliance (Sec 194O), and double-entry ledger in integer paise (no raw balance columns).
* Real-Time Bidding Engine: Open bidding with timers (10/15/30 min), counter-offers, ranking algorithm, and target push-fanout under 5 seconds.
* Return-Load Matching Engine: Rule-based algorithm calculating proximity, route vectoring, and soft-locking loads for approaching trucks within 40 km of drop-off.
* Third-Party Adapter Architecture: Clean adapter patterns with fallbacks for Mappls/Google Maps, SMS/WhatsApp (MSG91/Gupshup), KYC/OCR (Sarathi, VAHAN, PAN, GSTIN via Karza/Signzy), E-way bill GSPs, and Call Masking (Exotel).
Required Skills & Qualifications
* Mobile: Expert-level Flutter & Dart (background services, offline SQLite persistence, battery optimization, complex multilingual UI/fonts).
* Frontend: Senior React.js, TypeScript, WebSocket client management, responsive data-dense tables, and dashboards.
* Backend: Advanced NestJS (modular monolith design), TypeScript, BullMQ, and event-driven architectures.
* Databases & DevOps: PostgreSQL (schema design, row locking, partitioning), Redis, monorepo tooling, Docker, and GitHub Actions CI/CD pipelines.
* Fintech & Logistics Experience: Prior experience with escrow gateways, digital ledger systems, GPS tracking systems, or Indian logistics standards (Bilty, e-way bill, VAHAN/Sarathi) is a significant advantage.
Engagement Details
* Engagement Type: Contract / Freelance (Milestone-based or Dedicated Team per Sprint).
* Timeline: 15 two-week sprints (~7 months) to Closed Beta launch.
* Deliverables: Production-grade monorepo containing backend, 3 Flutter apps, 2 React web apps, tests, and CI/CD setup.
How to Apply
Please submit your proposal with:
* Links to past work, specifically complex Flutter applications, real-time tracking systems, or financial/marketplace platforms.
* An overview of whether you are applying as an individual specialist (Backend/Frontend/Mobile) or an integrated development team.
* Your availability and preferred engagement model (sprint-based fixed milestone vs. monthly rate).